<!DOCTYPE html>
<html>
<head>
	<title></title>
	<style type="text/css">
	*{margin:0;padding:0;}
	html{
		font-size:100px;
	}
	.box1{
		font-size:30px;
	}
	.box2{
		width: 2rem;
		font-size:100px;
	}
	.box3{
		width: 3em;
		background: red;
	}
	</style>
</head>
<body>


<div class='box1'>
	这是111111
	<div class='box2'>
		这是2222
		<div class='box3'>这是3333</div>
	</div>
</div>



</body>
</html>